I have a long text line with a lot of random words and numbers, i wish to assign a variable to the only 3 digit number in the line.
The number changes every different line but it is always only 3 digits. How does one search for the only 3 digit number in a linepython? There may be some 3 letter words so it must just be the number.
09824747 18 n 02 archer 0 bowman 0 003 @ 09640897 n 0000
in this example i want the variable digits = 003
asked Jun 12, 2013 at 13:54
JohnConneelyJohnConneely
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A regular expression with \b
word boundaries would do the trick:
re.findall[r'\b\d{3}\b', inputtext]
returns a list of all 3-digit numbers.
Demo:
>>> import re
>>> inputtext = '09824747 18 n 02 archer 0 bowman 0 003 @ 09640897 n 0000'
>>> re.findall[r'\b\d{3}\b', inputtext]
['003']
>>> inputtext = 'exact: 444, short: 12, long: 1234, at the end of the line: 456'
>>> re.findall[r'\b\d{3}\b', inputtext]
['444', '456']
answered Jun 12, 2013 at 13:58
Martijn Pieters♦Martijn Pieters
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You can use regular expressions. Or look for a digit, then check the next two characters manually.
I would use a regexp:
import re
threedig = re.compile[r'\b[\d{3}]\b'] # Regular expression matching three digits.
The \b
means "word boundary", and [\d{3}]
means "three digits", the parenthesis makes it a "group" so the matching text can be found.
Then search using:
mo = threedig.search["09824747 18 n 02 archer 0 bowman 0 003 @ 09640897 n 0000"]
if mo:
print mo.group[1]
The above prints 333
.
answered Jun 12, 2013 at 13:56
2
A solution thanks to regular expressions:
>>> s = "007 09824747 18 n 02 archer 0 bowman 0 003 @ 09640897 n 0000 008"
>>> r = re.findall[r'[?:[^\d]|\A][\d{3}][?:[^\d]|\Z]', s]
>>> r
['007', '003', '008']
answered Jun 12, 2013 at 14:01
EmmanuelEmmanuel
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In Python, I got the following to work [based on the answers above]:
re.compile['prefix\d{1,3}\suffix']}]
This covers the scenario for anywhere between 1-3 digits
answered Apr 30, 2018 at 17:15
raTMraTM
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Format a number to 3 digits in Python #
Use a formatted string literal to format a number to 3 digits, e.g. result = f'{my_int:03d}'
. The formatted string literal will format the number to the specified fixed length by adding leading zeros.
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from random import randint my_int = 5 # ✅ pad number with leading zeros [formatted-string literal] result = f'{my_int:03d}' print[result] # 👉️ '005' # ----------------------------------- # ✅ pad number with leading zeros [zfill] result = str[my_int].zfill[3] print[result] # 👉️ '005' # ---------------------------------- # ✅ get first 3 digits of number result = str[1234567][:3] print[result] # 👉️ 123 # ---------------------------------- # ✅ generate random 3 digit number result = randint[100, 999] print[result] # 👉️ 465 # ---------------------------------- # ✅ generate list of 3 digit numbers my_list = [f'{item:03d}' for item in range[10]] # 👇️ ['000', '001', '002', '003', '004', '005', '006', '007', '008', '009'] print[my_list]
The first example uses a formatted string literal to format a number to 3 digits by adding leading zeros.
Copied!
my_int = 5 result = f'{my_int:03d}' print[result] # 👉️ '005' print[f'{9:03d}'] # 👉️ 009
Formatted string literals [f-strings] let us include expressions inside of a string by prefixing the string with f
.
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my_str = 'The number is:' my_int = 137 result = f'{my_str} {my_int}' print[result] # 👉️ The number is: 137
Make sure to wrap expressions in curly braces - {expression}
.
Formatted string literals also enable us to use the format specification mini-language in expression blocks.
Alternatively, you can use the str.zfill[]
method.
Format a number to 3 digits using str.zfill[] #
To format a number to 3 digits:
- Use the
str[]
class to convert the number to a string. - Use the
str.zfill[]
method to format the number to 3 digits. - The
str.zfill[]
method will format the number to 3 digits by left-filling it with0
digits.
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my_int = 5 result = str[my_int].zfill[3] print[result] # 👉️ '005'
The str.zfill method takes the width of the string and left-fills the string with 0
digits to make it of the specified width.
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num = 13 result_1 = str[num].zfill[3] print[result_1] # 👉️ '013' result_2 = str[num].zfill[4] print[result_2] # 👉️ '0013'
Converting the number 13
to a string gives us a string with a length
of 2
.
Passing 3
as the width to the zfill[]
method means that the string will get left-filled with a single 0
digit.
If you need to get the first 3 digits of an integer, convert the integer to a string and use string slicing.
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result = str[1234567][:3] print[result] # 👉️ '123' my_int = int[result] print[my_int] # 👉️ 123
The slice goes from index 0
up to, but not including the digit at index 3
.
If you need to generate a random 3-digit number, use the randint[]
function.
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from random import randint result = randint[100, 999] print[result] # 👉️ 465
The
random.randint function takes 2 numbers - a
and b
as parameters and returns a random integer in the range.
Note that the range is inclusive - meaning both a
and b
can be returned.
If you need to generate a list of 3-digit numbers, use a list comprehension.
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my_list = [f'{item:03d}' for item in range[10]] # 👇️ ['000', '001', '002', '003', '004', '005', '006', '007', '008', '009'] print[my_list]
We used a list comprehension to iterate over a range of numbers.
List comprehensions are used to perform some operation for every element or select a subset of elements that meet a condition.
On each iteration, we use a formatted string literal to pad the current number with leading zeros to a length of 3.